This invention relates to the preparation of particulate polychloroprene. More particularly, the invention is a process for producing polychloroprene powders.
The polychloroprene powder can be used in substantially the same manner as prior crumb, and in addition, may be used in continuous automated processing. The powder has certain other advantages, however, since it requires less storage space because of the close packing of the particles. The powder is also free flowing, which makes it easier to transfer from the storage drums or sacks than the prior irregular crumb. The powder may also be employed in conventional molding techniques, used is dispersed form in suitable liquid carriers to apply coatings by roller coating, spray coating, and dip coating to a variety of substrates such as glass, ceramics, metal, wood, cloth, paper, paperboard and the like.
An earlier application, Ser. No. 571,957, filed Apr. 28, 1975, now U.S. Pat. No. 3,988,306, disclosed a process for producing particulate polychloroprene, especially powders comprising preparing a polychloroprene latex using a resin-type soap system, acidifying said latex, adding a minor amount of an alkyl sulfate salt to said latex, intimately mixing said latex with a coagulant solution, preferably adjusting the pH of the mixture of latex (slurry of rubber particles) and coagulant solution above 7, maintaining said mixture in a highly agitated state, recovering particulate polychloroprene and drying said particles. The alkyl sulfate was added to the latex after the polymerization reaction had been completed. The particular effectiveness of alkyl sulfate in substantially eliminating the agglomeration of the latex during coagulation is surprising.
In the process as described in the prior application, rather large amounts of base were required to reduce the acidity of the latex emulsion after the coagulation. Theoretically, any base could be used; however, since such large quantities of base were required, NaOH was effectively excluded because of the detrimental effect of the rubber of such massive amounts of Na ion. NH.sub.4 OH was the base of practical choice. Quite obviously, the amount of base required for pH adjustment would be reduced if the coagulation solution were removed from the latex and the latex suspended and/or washed in a fresh solution, such as demineralized water. However, decantation of the coagulant solution followed either by the addition of base or the addition of demineralized water and subsequent addition of base resulted in massive agglomeration.